The crack of thunder and lightning can send many animals, children and even adults scurrying for cover. Others love to watch and listen to thunderstorms, reveling in the awesome might and power displayed. This atmospheric condition is often used in movies and novels to create a dark and scary mood. Mood music uses the clap of thunder as a soothing rhythm to accompany the gentle sounds of rain. There’s no getting around it; thunderstorms garner great attention and tend to bring out strong emotions.
What is Lightning
While sometimes lightning happens during a volcanic eruption or a dust storm; the most common occurrence of lightning is during a thunderstorm. Lightning is a spark, an electrostatic discharge in the atmosphere. How lightning actually forms is still being studied by experts in the field. What is known is lightning can travel at extraordinary speeds of up to 140,000 miles per hour and generate heat of up to 54,000 degrees Fahrenheit. There are numerous hypothesis of how lightning is formed in clouds.
One hypothesis, the cloud particle collision, theorizes a collision and separation between ice crystals and a soft ice-water mixture cCredit: photo by R. Hadian, U.S. Geological Survey uploaded from Wikimedia Commonsalled graupel. During the collision, the ice crystals receive a positive charge transfer and the graupel receive a negative charge transfer. The ice crystals are lighter and are carried upwards to the top of the cloud where they increase the positive charge. Gravity brings the graupel to the middle and lower portions of the cloud where the negative charge accumulates. This pattern of charge and accumulation continues until it reaches sufficient electrical potential to discharge a bolt of lightning.
The establishment of electrical charge is evident in every hypothesis; the debate is strong when it comes to how the lightning is actually discharged. When the thundercloud moves along the surface of earth, a charge opposite to the bottom of the cloud is induced and follows the cloud. An initial path of ionized air starts from a negatively charged area of the cloud. These channels are called leaders. The negative and positive leaders move in different directions with the negatively charged leaders proceeding downward and may branch into a multiple paths. As the leader approaches the ground, the ground’s opposite charge increases the electrical field’s power.
Heinz Kasemir theorized if the electrical field was strong enough, a positive streamer can develop from the points on the ground; usually objects closest to the base of the cloud where the electrical field is strongest. As the field grows, the positive streamer can eventually connect to the descending leader and form a main discharge path. The established link of ionized air between the ground and the cloud becomes the path of least resistance and the earth’s greater current shoots back up the leader into the cloud. This is called the return stroke and is the brightest and most visible part of a lightning discharge.
What is Thunder
Long ago, philosophers theorized thunder was the sound of clouds colliding. As scientists studied the atmosphere, the theories evolved to define thunder as lightning creating a vacuum, to the current theory of lightning creates shock waves. Simply put, thunder is the sound made by lightning.
The current theory uses kinetic theory to explain the shock wave that creates the sound of thunder. The air along the discharge channel is superheated and as it expands outwards, collides with cooler air. The rapid increase of the gaseous molecules and the expansion outward from the lightning creates the shock wave heard as thunder. Credit: Brad Smull, NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL) uploaded from Wikimedia Commons
The rolling thunder effect is created because the shock wave occurs along the length of the path of lightning rather than one specific point. As lightning produces successive strokes, the thunder sound is prolonged. Distance to the lightning strike can be estimated because light travels faster than sound and the observer can time the intervals between the visible lightning and the sound of thunder. In normal conditions, the sound will travel approximately 1,130 feet per second. Therefore, a flash of lightning followed by thunder five seconds later would indicate a distance of approximately one mile. If the lightning is extremely close, the clap of thunder will occur almost simultaneously.
Fear of Thunderstorms
Although many people become scared when thunderstorms roll in; they are not necessarily dehabilitated with a phobia. The American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) describes a phobia as one in which there is a “marked and persistent fear” of a specific object or situation. The stimulus usually provokes an immediate response and may escalate into a panic attack. A phobia of thunderstorms may be exhibited by constant weather-watching, anxiety days ahead of a storm, unwillingness to leave home, and staying in the basement until the perceived danger is over, even if that is days later. While severe thunderstorms may require some precaution, those with a phobia go to extreme, often irrational measures.
In a study conducted by John Westefeld, the majority of participants reported the reason for their phobia was due to a traumatic childhood experience due to a severe storm. Most of the participants were embarrassed by their phobia and believed there were not many others with the same issue. Because of this factor, Westefeld suggests this is an underreported fear.
More common is the reaction by animals and children to the loud clap of thunder. Although various experts have theorized the reasons behind fear reaction from animals and children; little is known as to why exactly some animals and children fear thunderstorm while others delight in nature’s fireworks. Children may be responding to memories of past traumatic events of themselves or someone they love. If parents are fearful, the children and pets can sense this and it may cause anxiety. Pets may also be reacting to changes in barometric pressure, electrostatic activity or smells during a thunderstorm.
Thunder and lightning remain one of nature’s phenomena requiring further study to fully understand. As with tornadoes and hurricanes, floods and volcanoes, nature continues to produce events to frighten, awe and inspire humans.
Westefeld, John S. (1996, September). Severe weather phobia: An exploratory study. Journal of Clinical Psychology, 52 (5), 509-515.
American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision. Washington, D.C.: American Psychiatric Association, 2000.
www.Wikipedia.org accessed February 14, 2012
www.Peteducation.com accessed February 15, 2012
The copyright of the article “Understanding Thunder and Lightning” is owned by Cheryl Weldon and permission to republish in print or online must be granted by the author in writing.